The invention relates, in particular, to a method for reducing the energy consumption of a motor vehicle having an internal combustion engine and at least one vehicle electric system, to which at least a first electric consumer (also known as a load) is connected.
The number of electric consumers in motor vehicles has increased dramatically. In order to reduce the emission of CO2 in the vehicle, hydraulically operating consumers are being replaced increasingly by electric consumers. Thus, for example, one option is to replace the hydraulic steering of the motor vehicle with an electric power steering (EPS). However, such electric consumers can, in a short period of time, overtax the vehicle electric system with their high power demand. The result is that there is also a high demand that the electric system of the motor vehicle be stable. In particular, when high loads occur for a short period of time, adequately high electric voltage or rather electric power must be available.
There is therefore needed a method that makes it possible to achieve an efficient vehicle electric system with a reduced energy consumption of a motor vehicle.
This and other needs are met by a method and/or vehicle electric system for reducing the energy consumption of a motor vehicle having an internal combustion engine and at least a first electric consumer or load coupled to the vehicle electric system. The internal combustion engine is operated in a first operating mode at a first speed. In a second operating mode, the internal combustion engine is operated at a second speed that is higher than the first speed. A device, which is intended for detecting the driving situation and is provided in the vehicle, recognizes an imminent specific driving situation on the basis of the previous behavior of the driver in controlling the vehicle and/or the behavior of the vehicle in advance, and initiates a switch in the internal combustion engine from the first operating mode to the second operating mode. Advantageous embodiments of the invention are described herein.
One aspect of the invention consists of the fact that the internal combustion engine is operated in a first operating mode at a first speed. For example, both the electric generator of the vehicle and the battery of the vehicle feed jointly the vehicle electric system in order to supply the electric consumers with an adequate electric voltage. In the first operating mode the generator can be loaded to full capacity.
In a second operating mode, the internal combustion engine is operated at a second speed that is higher than the first speed.
A device, which is intended for detecting the driving situation and is provided in the vehicle, recognizes an imminent specific driving situation on the basis of the previous behavior of the driver in controlling the vehicle and/or the behavior of the vehicle in advance and initiates a switch in the internal combustion engine from the first operating mode to the second operating mode. Therefore, the invention provides that the recognition of an imminent specific driving situation produces an increase in the speed of the internal combustion engine that serves to stabilize the voltage of the vehicle electric system when this voltage is actually required on short notice. An inventive increase in the speed can be practical especially in the idling range of the internal combustion engine between, for example, approximately 500 and 1,400 revolutions per minute. A permanently higher speed or the idling speed of the internal combustion engine that has a negative impact on consumption and is intended to compensate for a sudden additional load on the vehicle electric system can be avoided by means of the solution of the invention.
One embodiment of the invention provides that on operating the internal combustion engine in the second operating mode, the device for detecting the driving situation compares the speed of the internal combustion engine with a predetermined desired speed and on undershooting the desired speed initiates an increase in the speed of the internal combustion engine to at least the desired speed. These inventive measures can counter a varying load on the vehicle electric system, and the working range of the electric generator can be returned to a range having a better efficiency level.
One embodiment of the invention provides that the device for detecting the driving situation takes into consideration who the current driver is and what his previous behavior was. In this way, the hit rate for predicting that a cornering action is imminent can be raised. If, for example, the device for detecting the driving situation recognizes that the driver in question always swerves during a cornering action (a maneuver that is not always done by every driver), this criterion can be weighted higher in the algorithm for recognizing a cornering action.
One embodiment of the invention provides that the first electric consumer is an electrically operated steering system of the motor vehicle and the imminent specific driving situation is a cornering action. Especially during a cornering action it is important for the driver that the behavior of the steering system be not adversely changed or that the steering not become stiff. During a cornering action the power requirement of an electric steering system is especially high.
One embodiment of the invention provides that the position of the accelerator pedal (also referred to herein as a driving pedal or gas pedal) is detected by the device for detecting the driving situation, and the operating mode of the internal combustion engine is switched from the first operating mode to the second operating mode, when the pedal is located largely in its rest position, and at least one additional driving situation occurs. Even this feature is a characteristic of an imminent cornering action and yields an important indicator of an imminent cornering action.
A further development of the invention provides that the acceleration and the speed of the vehicle are detected by the device for detecting the driving situation, and the operating mode of the internal combustion engine is switched from the first operating mode to the second operating mode, when the acceleration of the vehicle is negative, the speed falls below a predetermined threshold value, and at least one additional driving situation occurs. This feature, too, is characteristic of an imminent cornering action and furnishes an important indicator of an imminent cornering action.
A preferred embodiment of the invention provides that the device for detecting the driving situation checks whether the vehicle is making a swerving maneuver. Driving in swerving mode can give a very clear sign of an imminent cornering action.
In one embodiment of the invention, the steering angle of the electric steering system of the vehicle is detected by the device for detecting the driving situation. The operating mode of the internal combustion engine is switched from the first operating mode to the second operating mode, when the absolute value of the steering angle is greater than the predetermined threshold value, and at least one additional driving situation occurs. This feature may be an indicator that the driver is beginning to make a swerving maneuver or rather a cornering maneuver.
An additional embodiment of the invention provides that the steering angle of the electric steering system of the vehicle is detected by the device for detecting the driving situation, and the operating mode of the internal combustion engine is switched from the first operating mode to the second operating mode, when the absolute value of the steering angle is greater than a predetermined speed-dependent steering threshold or rather steering angle threshold, and at least one additional driving situation occurs. If the driver does not swerve prior to a cornering action, this characteristic of an imminent cornering action may replace the “swerving criterion” and may raise the reliability of the prediction of an imminent cornering action.
A further development of the invention provides that the device for detecting the driving situation checks whether the brake pressure is higher than a predetermined brake pressure or rather a tolerance pressure and, in addition, checks whether the speed is less than a predetermined acceleration-dependent speed value and/or a dynamic cornering threshold. In this way the reliability of the prediction of a cornering action can be increased even more.
In addition, the invention proposes a vehicle electric system of a motor vehicle that exhibits a program-controlled device, which is intended for detecting the driving situation and carries out the method of the invention. Furthermore, the invention proposes a program-controlled device, which is intended for detecting the driving situation and which carries out the method of the invention or initiates its execution.
The inventive method is described in detail below with reference to the flow charts using a cornering action as an example. Identical reference numerals and symbols show the same functions or functions that have the same effect.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.